The present invention relates to a method for texturing substrate surfaces by means of ion implantation processing, e.g., substrates utilized in the manufacture of magnetic recording media, and to magnetic media obtained thereby. The invention has particular utility in texturing the CSS landing zone of hard disk magnetic media such as are employed in computer-related applications.
Hard disk-type magnetic media are widely utilized in various applications, particularly in the computer industry. A conventional longitudinal recording, hard magnetic disk-type medium 1 commonly employed in computer-related applications is schematically depicted in FIG. 1, and comprises a substantially rigid, non-magnetic metal substrate 10, typically of an aluminum (Al) alloy, such as an aluminum-magnesium (Alxe2x80x94Mg) alloy, having sequentially deposited thereon a plating layer 11, such as of amorphous nickel-phosphors (Nixe2x80x94P); an amorphous seed layer 12A, e.g., of NiAl; a polycrystalline underlayer 12B, typically of chromium (Cr) or a Cr-based alloy; a magnetic layer 13, e.g., of a cobalt (Co)-based alloy; a protective overcoat layer 14, typically containing carbon (C), e.g., diamond-like carbon (xe2x80x9cDLCxe2x80x9d) formed, as is known, by sputtering of a carbon target in an appropriate atmosphere or by ion beam deposition (xe2x80x9cIBDxe2x80x9d) utilizing appropriate precursor gases; and a lubricant topcoat layer 15, typically of a perfluoropolyether compound applied, as is known, by dipping, spraying, etc. The magnetic layer 13, typically comprised of a Co-based alloy, may be formed by sputtering techniques and includes polycrystallites epitaxially grown on the polycrystalline Cr or Cr-based alloy underlayer 12B.
In operation of medium 1, the magnetic layer 13 can be locally magnetized by a write transducer, or write xe2x80x9cheadxe2x80x9d, to record and thereby store information therein. The write transducer or head creates a highly concentrated magnetic field which alternates direction based on the bits of information to be stored. When the local magnetic field produced by the write transducer is greater than the coercivity of the material of the recording medium layer 13, the grains of the polycrystalline material at that location are magnetized. The grains retain their magnetization after the magnetic field applied thereto by the write transducer is removed. The direction of the magnetization matches the direction of the applied magnetic field. The magnetization of the recording medium layer 13 can subsequently produce an electrical response in a read transducer, or read xe2x80x9cheadxe2x80x9d, allowing the stored information to be read.
Thin film magnetic recording media are conventionally employed in hard disk form for use with disk drives for storing large amounts of data in magnetizable form. Typically, one or more disks are rotated about a central axis in combination with data transducer heads. In operation, a typical contact start/stop (xe2x80x9cCSSxe2x80x9d) method commences when the transducer head, carried by an air-bearing slider, begins to slide against the surface of the disk as the disk begins to rotate. Upon reaching a predetermined high rotational speed, the head floats in air at a predetermined distance from the surface of the disk due to dynamic pressure effects caused by the air flow generated between the sliding surface of the head and the disk. During reading and recording operations, the transducer head is maintained at a controlled distance from the recording surface, supported on a bearing of air as the disk rotates, such that the head can be freely moved in both the circumferential and radial directions, allowing data to be recorded on and retrieved from the disk at a desired position. Upon terminating operation of the disk drive, the rotational speed of the disk decreases and the head again begins to slide against the surface of the disk and eventually stops in contact with and pressing against the surface of the disk. Thus, the transducer head contacts the disk surface whenever the disk is stationary, accelerated from the static position, and during deceleration just prior to completely stopping. Each time the head and disk assembly is driven, the sliding surface of the head repeats the cyclic sequence consisting of stopping, sliding against the surface of the disk, floating in air, sliding against the surface of the disk, and stopping.
The air bearing design for the head slider/transducer utilized for CSS-type operation as described above provides an interface between the slider and the disk which prevents damage to the disk over the life of the disk/slider/transducer head system, and provides damping in the event the disk drive system undergoes mechanical shock due to vibrations of external origin. The air bearing also provides the desired spacing between the transducer and the disk surface. A bias force is applied to the slider by a flexure armature in a direction toward the disk surface. This bias force is counter-acted by lifting forces from the air bearing until an equilibrium state is achieved. The slider will contact the disk surface if the rotating speed of the disk is insufficient to cause the slider to xe2x80x9cflyxe2x80x9d, as during startup and shut-down phases of the CSS cycle. If the slider contacts a data region of the disk, the data may be lost and the disk permanently damaged.
Referring now to FIG. 2, shown therein in simplified, schematic perspective view, is a conventionally configured magnetic hard disk 30 having a CSS (i.e., xe2x80x9clandingxe2x80x9d) zone 36 and a data (i.e., recording) zone 40. More specifically, FIG. 2 illustrates an annularly-shaped magnetic hard disk 30 including an inner diameter 32 and an outer diameter 34. Adjacent to the inner diameter is an annularly-shaped, inner CSS or xe2x80x9clandingxe2x80x9d zone 36. When disk 30 is operated in conjunction with a magnetic transducer head (not shown in the drawing), the CSS or xe2x80x9clandingxe2x80x9d zone 36 is the region where the head makes contact with the disk surface during the above-described start-stop cycles or other intermittent occurrences. In FIG. 2, the radially outer edge of the CSS or xe2x80x9clandingxe2x80x9d zone 36 is indicated by line 38, which is the boundary between CSS zone 36 and data zone 40 where information in magnetic form is stored within the magnetic recording medium layer of disk 30.
It is generally considered desirable for reliably and predictably performing reading and recording operations, and essential for obtaining high areal density magnetic recording, that the transducer head be maintained as close to the disk surface as possible in order to minimize its flying height. Thus, a smooth disk surface is preferred, as well as a smooth opposing surface of the transducer head, thereby permitting the head and the disk to be positioned in very close proximity, with an attendant increase in predictability and consistent behavior of the air bearing supporting the transducer head during motion. However, if the head surface and the recording surface are too flat, the precision match of these surfaces gives rise to friction and xe2x80x9cstictionxe2x80x9d, i.e., a combination of friction and xe2x80x9cstickinessxe2x80x9d (resulting from viscous shear forces) at the disk surface which causes the transducer head to adhere to the surface, particularly after periods of non-use, thereby making it more difficult for the transducer head to initiate movement therefrom. Excessive stiction and friction during the start-up and stopping phases of the above-described cyclic sequence causes wear of the transducer and disk 25 surfaces, eventually leading to what is referred to as xe2x80x9chead crashxe2x80x9d. Another drawback associated with smooth disk surfaces is lack of durability resulting from the very small amount of lubricant which is retained thereon. Thus, there are competing goals of minimizing transducer head flying height (as by the use of smooth surfaces) and reducing transducer head/disk friction (as by avoiding use of smooth surfaces).
Conventional practices for addressing these apparent competing objectives include providing at least the CSS or xe2x80x9clandingxe2x80x9d zone of the magnetic disk recording medium with a roughened surface to reduce transducer head/disk friction and stiction by a number of different techniques generally known as xe2x80x9ctexturingxe2x80x9d, such as disclosed in U.S. Pat. Nos. 5,626,941; 5,635,269; 5,714,207; 5,718,811; 5,768,076; 5,798,164; 5,945,197; and 6,020,045, the entire disclosures of which are incorporated herein by reference. Referring again to FIG. 1, suitable texturing techniques include, inter alia, circumferential polishing and localized laser heating of the surface of the disk substrate 10 (e.g., of Alxe2x80x94Mg alloy) to create thereon a texture pattern comprising a plurality of spaced apart projections (xe2x80x9cbumpsxe2x80x9d) prior to deposition thereon of a layer stack comprised of plating layer 12, polycrystalline seed or underlayer 12, magnetic layer 13, protective overcoat 14, and lubricant topcoat 15, wherein the textured surface of the underlying disk substrate 10 is substantially replicated in the subsequently deposited, overlying layers. According to such methodology, by providing a textured surface in at least the CSS or xe2x80x9clandingxe2x80x9d zone, the transducer head is able to rest and slide on the peaks of the projections or xe2x80x9cbumpsxe2x80x9d during starting and stopping, thereby reducing the area of contact between the transducer head and the magnetic medium. As a consequence of the reduced area of contact in the CSS or xe2x80x9clandingxe2x80x9d zone, the amount of force necessary to initiate movement of the transducer head is considerably reduced. An additional advantage provided by the textured disk surface is the ability to retain a greater amount of lubricant, thereby further increasing disk durability by reducing friction and stiction.
A variety of possible configurations of the textured surface approach for reducing stiction and friction between the transducer head and the disk surface are possible, including texturing only the CSS or xe2x80x9clandingxe2x80x9d zone, wherein specular smoothness of the data zone is retained for permitting high bit density recording by allowing for very low head flying height; texturing the entire disk surface, i.e., the CSS and data zones, whereby friction and stiction reduction is provided in the data zone in addition to the CSS zone; and separately (i.e., differently) textured CSS and data zones, with and without a transition zone between the differently textured zones, wherein the texturing is optimized for each type of zone to maximize both recording characteristics and mechanical durability.
As previously indicated, in magnetic data/information recording, storage, and retrieval technology, it is continually desired to improve the areal density at which data/information can be recorded and reliably read. Because the recording density of a hard disk and its associated drive mechanism is limited by the distance between the transducer head and the surface of the magnetic medium, a goal of air bearing slider design for use in CSS operation, as described above, is to xe2x80x9cflyxe2x80x9d the slider as closely as possible to the medium surface while avoiding physical contact or impact with the medium. Smaller spacings, or xe2x80x9cfly heightsxe2x80x9d, are desired so that the transducer head can distinguish between the various magnetic fields emanating from closely spaced regions on the data zone of the disk surface.
The design of the CSS, or landing zone, of advanced, high areal recording density magnetic hard disk media for use with sliders operating at very low flying heights, i.e., 0.7 xcexc inch or less, poses a challenge because the conventional laser zone texturing (xe2x80x9cLZTxe2x80x9d) technique appropriate for non-padded head sliders is fast approaching its technical limit in that further reduction in bump height to below about 130 xc3x85, e.g., in order to provide lower flying heights of about 0.5 xcexc inch, will inevitably incur stiction failures due to onset of stiction xe2x80x9cavalanchexe2x80x9d. Stated somewhat differently, stiction cannot be adequately controlled (i.e., moderated) for transducer head sliders operating at such low flying heights, unless relatively tall laser bumps, i.e., greater than about 130 xc3x85, are employed. However, use of such tall bumps entails an increased likelihood of head-disk interference which can result in catastrophic head-disk failures, such as crashes.
As is evident from the foregoing, it is essential that the laser bump geometry be optimized for stiction, friction, and durability of the transducer head-media interface. Specifically, a laser bump height which is too low may result in a high rate of stiction-related failure, whereas a laser bump height which is too high may reduce media durability. The requirements (xe2x80x9cspec limitsxe2x80x9d) on the laser bump height become increasingly stringent as the transducer head-to-media spacing is decreased in order to increase areal recording density. At the same time, the laser texturing process itself determines the tolerance of laser bump height control, the latter having already been optimized and which cannot be further improved without incurring additional capital investment in the laser processing system. Thus, as the laser bump height xe2x80x9cspec rangexe2x80x9d approaches the manufacturing tolerance, an increasing amount or proportion of the produced laser bumps will fail to be within the xe2x80x9cspec limitsxe2x80x9d and either cause stiction failures (at low bump heights) or durability failures (at high bump heights).
The above-described mismatch between process capability and tolerance requirements effectively limits the ability to extend the laser zone texture (LZT)-based CSS technology in the fabrication of very high areal recording density magnetic media. In addition to this, it is considered essential that for further significant increase in areal recording density to be realized, perpendicular rather than longitudinal media (i.e., media where the orientation direction of magnetization of the individual grains of the magnetic recording layer is perpendicular rather than parallel to the longitudinal direction of the media) must be utilized, as well as glass-based rather than conventional NiP-plated, Al-based substrates. However, in addition to being limited by the same laser bump height tolerance control as conventional NiP-plated, Al-based substrates, functionally suitable laser texturing of glass-based substrates will require substantial new capital investment in infra-red (IR) lasers and may also incur severe, if not fatal, corrosion-associated problems if multi-phase crystalline glass substrates are utilized.
In view of the foregoing, there exists a need for an improved method for texturing at least the surface of the CSS zone of a magnetic recording medium or substrate therefor, which method substantially eliminates or entirely avoids the above-described drawbacks and disadvantages associated with LZT processing. In addition, there exist a need for high areal recording density magnetic media in disk form and which include an improved textured CSS or landing zone.
The present invention addresses and solves problems attendant upon the manufacture of high areal recording density magnetic hard disk media with textured CSS or landing zones for use with read/write transducers in the form of head sliders operating at very low glide heights, while maintaining full compatibility with all mechanical aspects of conventional hard disk drive technology. Moreover, manufacture and implementation of the present invention can be obtained at a cost comparable to that of existing automated technology for the fabrication of hard disk magnetic recording media.
An advantage of the present invention is an improved method of texturing a surface of a substrate.
Another advantage of the present invention is an improved method of texturing a CSS or landing zone of a an annular disk-shaped substrate for a hard disk magnetic recording medium for reducing stiction and friction of the medium when utilized with a read/write transducer operating at a very low flying height.
Yet another advantage of the present invention is an improved substrate for a hard disk magnetic recording medium which includes an ion-implanted, surface-textured CSS or landing zone.
Still another advantage of the present invention is an improved hard disk magnetic recording medium which includes an ion-implanted, surface-textured CSS or landing zone.
Additional advantages and other aspects and features of the present invention will be set forth in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present invention. The advantages of the present invention may be realized and obtained as particularly pointed out in the appended claims.
According to an aspect of the present invention, the foregoing and other advantages are obtained in part by a method of texturing a surface of a substrate, comprising steps of:
(a) providing a substrate having a surface;
(b) providing a mask in overlying relation to the substrate surface, the mask comprising a layer of a material including a patterned plurality of openings extending therethrough;
(c) bombarding the mask with ions to selectively implant the ions in portions of the substrate surface aligned with and selectively exposed by the patterned plurality of openings, whereby the height of the selectively ion-implanted portions of the substrate surface is increased or decreased relative to the height of non-ion-implanted portions of the substrate surface, thereby providing the substrate surface with a texture pattern corresponding to the patterned plurality of openings extending through the mask.
According to embodiments of the present invention, step (a) comprises providing a non-magnetic substrate for a hard disk magnetic recording medium, the substrate including at least one major surface having a contact start/stop (CSS) or landing zone and a data zone; and in accordance with certain alternative embodiments of the present invention, step (a) comprises providing a nonmagnetic substrate wherein the substrate surface is bare or is covered by at least one layer of a laminate of layers comprising the magnetic recording medium.
Embodiments of the present invention include the step (a) of providing a non-magnetic substrate comprised of a material selected from the group consisting of Al, Al/NiP, Al-based alloys, other metals, other metal alloys, polymers, and polymer-based materials, or a high modulus, hard-surfaced material selected from the group consisting of glass, ceramics, and glass-ceramics.
According to a particular embodiment of the present invention, step (a) comprises providing an annular disk-shaped substrate wherein the CSS or landing zone comprises an annularly-shaped zone adjacent an inner or outer diameter of the disk and the data zone comprises an annularly-shaped zone radially adjacent the CSS or landing zone; step (b) comprises providing the mask in overlying relation to the substrate surface such that the patterned plurality of openings extending therethrough selectively expose portions of the substrate surface comprising the CSS or landing zone, whereby the substrate surface in the CSS or landing zone is selectively provided with a texture for minimizing stiction and friction when utilized with a read/write transducer operating at a low flying height over the surface.
In accordance with alternative embodiments of the present invention, step (b) comprises providing a contact mask or a non-contacting projection mask.
According to a particular embodiment of the present invention, step (b) comprises providing a mask wherein each of the patterned plurality of openings has a maximum lateral dimension in the range from about 0.1 to about 50 xcexcm and adjacent openings are spaced apart from about 0.1 to about 50 xcexcm; step (c) comprises implanting the ions into the selectively exposed portions of the substrate surface in the CSS or landing zone to increase or decrease the height of the selectively ion-implanted portions from about 1 to about 100 xc3x85 relative to the height of the non-ion-implanted portions of the substrate surface in the CSS or landing zone, the change in height being determined by selection of the substrate material and ion species, dosage, and energy.
In accordance with embodiments of the present invention, step (c) comprises bombarding the mask with ions of sufficient energy so as to substantially avoid or at least minimize sputtering of the selectively ion-implanted portions of the substrate surface in the CSS or landing zone; e.g., step (c) comprises implanting at least one ion species selected from among rare gas ions (He, Ne, Ar, Xe, and Kr), H, B, C, and N ions, at an implantation energy and dosage from about 1 keV to about 10 MeV and from about 1012 to about 1018 ions/cm2, respectively.
According to a particular embodiment of the present invention, step (a) comprises providing a non-magnetic, annular disk-shaped substrate for a magnetic recording medium, the substrate including at least one major surface having a contact start/stop (CSS) or landing zone and a data zone, the CSS or landing zone comprising an annularly-shaped zone adjacent an inner or outer diameter of the disk and the data zone comprising an annularly-shaped zone radially adjacent said CSS or landing zone;
step (b) comprises providing a mask in overlying relation to the substrate surface such that the patterned plurality of openings extending therethrough selectively expose portions of the substrate surface comprising the CSS or landing zone; and
step (c) comprises implanting the ions into the selectively exposed portions of the substrate surface in the CSS or landing zone to increase or decrease the height of the selectively ion-implanted portions relative to the height of the non-ion-implanted portions of the substrate surface in the CSS or landing zone, whereby the substrate surface in the CSS or landing zone is selectively provided with a texture for minimizing stiction and friction when utilized with a read/write transducer operating at a low flying height over the surface, wherein:
step (a) comprises providing a substrate comprised of a material selected from the group consisting of Al, Al/NiP, Al-based alloys, other metals, other metal alloys, polymers, and polymer-based materials, or a high modulus, hard-surfaced material selected from the group consisting of glass, ceramics, and glass-ceramics, the substrate surface being bare or covered by at least one layer of a laminate of layers comprising the magnetic recording medium;
step (b) comprises providing a mask wherein each of the patterned plurality of openings has a maximum lateral dimension in the range from about 0.1 to about 50 xcexcm and adjacent openings are spaced apart from about 0.1 to about 50 xcexcm;
and step (c) comprises implanting the ions into the selectively exposed portions of the substrate surface in the CSS or landing zone to increase or decrease the height of the selectively ion-implanted portions from about 1 to about 100 xc3x85 relative to the height of the non-ion-implanted portions of the substrate surface in the CSS or landing zone, the change in height being determined by selection of the substrate material and species, dosage, and energy of the implanted ions, the energy of the implanted ions being sufficient to substantially avoid or at least minimize sputtering of the selectively ion-implanted portions of the substrate surface in the CSS or landing zone.
Another aspect of the present invention is a hard disk magnetic recording medium manufactured according to the above method.
Yet another aspect of the present invention is a non-magnetic substrate for a hard disk magnetic recording medium, comprising:
a non-magnetic annular disk, the annular disk including at least one major surface having a contact start/stop (CSS) or landing zone and a data zone, the CSS or landing zone comprising an annularly-shaped zone adjacent an inner or outer diameter of the disk and the data zone comprising an annularly-shaped zone radially adjacent the CSS or landing zone; wherein the substrate surface in the annularly-shaped CSS or landing zone is textured and includes a patterned plurality of spaced-apart, ion-implanted bumps or depressions for decreasing stiction and friction when the substrate forms part of a hard disk magnetic recording medium utilized with a read/write transducer operating at a very low flying height.
According to certain embodiments of the present invention, each of the patterned plurality of spaced-apart, ion-implanted bumps or depressions for decreasing stiction and friction has a height or depth in the range from about 1 to about 100 xc3x85, a maximum lateral dimension in the range from about 0.1 to about 50 xcexcm, and a spacing between adjacent bumps in the range from about 0.1 to about 50 xcexcm; and the annular disk comprises a non-magnetic material selected from the group consisting of Al, Al/NiP, Al-based alloys, other metals, other metal alloys, polymers, and polymer-based materials, or a high modulus, hard-surfaced material selected from the group consisting of glass, ceramics, and glass-ceramics.
Still another aspect of the present invention is a hard disk magnetic recording medium comprising the substrate as formed above, further including a laminate of layers overlying the data zone, the laminate including at least one magnetic recording layer.
Yet another aspect of the present invention is a hard disk magnetic recording medium, comprising:
(a) a non-magnetic substrate; and
(b) means for reducing stiction and friction of a CSS or landing zone of the medium.
According to an embodiment of the invention, the non-magnetic substrate is an annular disk and the CSS or landing zone forms an annularly-shaped zone adjacent an inner or outer diameter of the disk.